YSI 52 - Manual (Page 11)

Calibration Section 3
4. When you have adjusted the reading to the desired value (let’s say you chose 98.0%),
press CONFIRM. The instrument will display the legend “Please wait” for a few seconds.
Then it will display:
C a l i b r a t e d t o
9 8. 0 %
You are now ready to measure dissolved oxygen.
3.4 CALIBRATION IN AIR-SATURATED WATER
A second alternative for calibration is to calibrate in air-saturated water. This procedure
is the same as the procedure for calibration in air except that the calibration medium is
saturated water rather than saturated air.
To calibrate in air-saturated water:
1. Air-saturate a volume of water (300 to 500 mL) by aerating for at least 15 minutes at a
relatively constant temperature.
2. Place the probe in the sample and provide adequate stirring (at least 1 foot per second).
Switch to O
2
-TEMP and observe temperature and oxygen readings for stability. It may
take 5 minutes for the temperature to come to equilibrium. If you have just turned the
instrument on, allow 15 minutes for the system to equilibrate.
3. Switch to CALIBRATE, select percent calibration, then adjust the number in the
display to the correct value based on current barometric pressure or altitude and press
CONFIRM.
3.5 CALIBRATION BY WINKLER TITRATION
A third alternative for calibration is to calibrate to a known oxygen value determined by a
Winkler titration.
To calibrate using a Winkler-titrated sample:
1. Determine the dissolved oxygen value of a sample by Winkler titration.
2. Place the probe in the sample and provide adequate stirring (at least 1 foot per second).
Switch to O
2
-TEMP and observe temperature and oxygen readings for stability.
YSI, Incorporated Model 52 7